The present invention relates to aqueous compositions for cleaning contact lenses, particularly soft contact lenses.
Deposits such as proteins, lipids and calcium are formed on contact lenses when these lenses are worn on the eye. Proteins adsorb to almost all surfaces and the minimization or elimination of protein adsorption has been the subject of numerous studies and technologies. The removal of proteins from a contact lens is required due to the irritation and discomfort that result from the buildup of deposits on the surface of the lens.
Various compositions and methods have been utilized to clean contact lenses prior to the present invention. The prior compositions and methods have included cleaning agents such as surfactants, chelating agents and proteolytic enzymes. The present invention is particularly directed to the removal of protein deposits from contact lenses. The principal component of such deposits is lysozyme.
Lysozyme is one of the major proteinaceous components in human tears. It is an enzyme that acts as an antimicrobial agent by degrading glycosidic linkages between N-acetylmuramic acid and N-acetylglucosamine units of the microbial cell wall. Thus, the presence of lysozyme in human tears is a natural defense mechanism against ocular infections. Unfortunately, when contact lenses are placed on the eye, prolonged bathing of the lenses by the tears leads to deposits of lysozyme on the lenses. Lysozyme is a protein, and the deposits of lysozyme on contact lenses are typically composed of a mixture of proteins, lipids and other materials. These deposits become bound to the lenses, and consequently are very difficult to remove.
The use of proteolytic enzymes (e.g., pancreatin) to remove protein deposits from contact lenses has been fairly effective. However, the treatment of contact lenses with cleaning compositions containing proteolytic enzymes is considered by some contact lens wearers to be undesirable, in view of cost, convenience and other factors. Consequently, the use of proteolytic enzyme products to remove protein deposits from contact lenses has declined greatly over the past decade. The enzyme products have largely been replaced by complexing agents contained in “multi-purpose” solutions that are used to clean and disinfect contact lenses on a daily basis. For example, U.S. Pat. No. 5,858,937 (Richard, et al.) describes the use of phosphonates in multi-purpose solutions to remove protein deposits. Although multi-purpose solutions containing such complexing agents have been commercially successful, there is a need for improved solutions, particularly solutions that are more effective in preventing and removing protein deposits. The present invention addresses this need.